RF input port bias?

Does anybody know what the bias requirement is for the differential input ports on the RF-Inputs of the LMS7002M ?
The LimeSDR default circuit has them all DC blocked (is this necessary?), but the optimized broadband HF matching network by Danny Webster has it DC grounded. ( https://myriadrf.org/blog/optimising-limesdr-matching-hf/ ). I can’t seem to find a statement in the LMS7002M datasheet that declares this.

Also, the schematic representation for the T3 & T5 input transformers show a Mini-Circuits TC1-1-13MA+ part. The data sheet for this part shows that it is not center-tapped as shown on the LimeSDR schematic. In addition, it is more of a 1:1 balun arrangement. Pin 6 and 4 are one winding and 1 and 3 are the other. If this is true, the ground on pin 4 is carried through (DC wise) to the “rfgn_l_REF_1” pin if using Danny’s circuit. The other differential input is DC connected through the 82 Ohm resistor between the input pins.

Hello DrNefario,

Inputs to the LMS7002M receiver are all internally AC coupled.

T3 and T5 input transformers are not centered taped, since pin 2 on the TC1-1-13MA+ part is “NOT USED” (also seen in the “Config. G” picture in the part datasheet).


Thank you Karolis. Yes I did see that in the TC1-1-13MA+ part datasheet.
So, if the LMS7002M receiver inputs are all internally AC coupled, could you please comment on what the maximum DC limit is on those pins?